Here is a
simple triangle/squarewave generator using a common 1458 dual op-amp
that can be used from very low frequencies to about 10 Khz. The time
interval for one half cycle is about R*C and the outputs will supply
about 10 milliamps of current. Triangle amplitude can be altered by
adjusting the 47K resistor, and waveform offset can be removed by
adding a capacitor in series with the output.